7339

• UCREFRP Catalog Number: 7339
• Author: Valdez, R. A.
• Title: A Review of the Hatchery Program for Threatened and Endangered Fishes of the Colorado River.
• USFW Year: 1985.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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3-10

weight at 24-hour intervals (Hamman 1982b).

Li ke humpback chub, bonyta il exhi bi t fi ne tubercl es on the head,
opercles and the paired fins. Breeding males are light orange at the base
of the paired fins but no prenuptual color was noted on the females (Hamman
1982b) .

When eggs are ready to be expelled, the vent area of each anesthetized
female is wiped clean and the eggs stripped into a plastic pan. Milt from a
mal e is added and the mi xture dil uted with water to activate the sperm. The
eggs are stirred and washed for about 45 minutes with a feather to prevent
clumping and enhance water hardening. The eggs are then poured on screen
trays covered with hardware cloth and placed in aluminum recirculating
troughs.

Eggs incubated at three water temperatures at Dexter NFH in 1981 showed
dramatically different incubation times and viability (Hamman 1982b). Egg
in 20-21 oC, 16-17 oc and 12-13 oc hatched in 99-174 hours, l70-269 hours
and 334-498 hours, respectively. The average length of newly-hatched fry at
these three temperatures was 6.8 mm TL, and hatching success was greatest at
20-21 Oc (88-91%).

The fecundity of bony tails is considerably higher than that of the
humpback chub. Five females hand-stripped at Willow Beach NFH in 1981
(Hamman 1982b) yielded 5,850 to 37,700 eggs per female for an average of
25,090 eggs per fish, or 21,514 eggs per kg of body weight.

Bonyta il at the Wi 11 ow Beach NFH in 1981 grew from average 1 engths of
6.8 mm to 49.5 mm TL and average weights of 2.8 mg to 974.6 mg per fish in
70 days. The fi sh were fi rst fed a commerci al trout starter and 1 ater fed
pelleted fish food.

At Dexter NFH in 1983, two wild females yielded 50,096 and 35,376 eggs,
while 24 two-year olds yielded 1,015 to 10,384 eggs per fish for a mean of
4,677. Average number of eggs per pound was 5,075 to 29,930 with a mean of
17,280 (Jensen 1983b).

In 1984 at Dexter, 11 three-year old female bony tail produced 23,940
eggs per pound of body weight with a mean fecundity of 16,464 eggs per
females (Jensen 1984).

3.4 Razorback Sucker

3.4.1 Brief History

Although the razorback sucker is not an endangered species, its status
as a candidate has prompted considerable attention from the hatchery
program. The fi rst known transfer of wi 1 d adul t razorbacks to a hatchery
was on March 27, 1974, when a joint Federal-State Recovery Team collected 40
adul ts near Cottonwood Cove, Lake Mohave. Some eggs were stri pped on si te
and moved with some fish to Willow Beach NFH. Thirty-two of these adults
were later transferred to the Arizona State Fish Hatchery at Page Springs on
May 7, 1974. In January of 1981 and 1982, 134 and 147 wild adul ts,
respectively, from Lake Mohave were transferred to Dexter NFH to provi de